But when lab-reared adults were released into a coffee plantation during a trial program, only one percent of the population stayed put.

In 2005 Barrera and colleagues reported that C. stephanoderis releases a fecal-smelling chemical called skatole when agitated.

Hardy surmises that the lab-reared wasps were agitated during the bumpy ride from the lab to the field and were releasing skatole.

When the jar was opened, the strong chemical signal drove the wasps away.

In contrast, when wasp pupae were set in the coffee plantation and the insects emerged naturally, four percent of the wasps stayed.

Chemical release, Hardy said, is "probably a very strong candidate explanation for why they get a better ratio of establishment in the field when [the wasps] emerge naturally rather than [after being] shaken about."